This is vaguely okay but makes the common mistake of overemphasizing that codecs use an IDCT. That's just a component of intra-prediction, it isn't necessarily important or used, and in H.264+ it isn't even a real IDCT when it is used. It's a simpler transform that isn't mathematically accurate but is bit-exact, which is more important.
I remember back in the day when doom9 was blocked at the corp firewall level because it had posts on how to circumvent things. Nevermind it was the unofficial support for things like AVISynth, x264, etc. Even the nascent days of ffmpeg were there. It took a lot of cajoling and back and forth with legal depts, but eventually, was allowed to be granted access on an individual basis
I owe a lot of what was accomplished to folks like DG and the other troopers from the bad ol' days of VFW based apps. It was like monkeys throwing rocks at the space ships compared to whats now. Remember when 2 cores was fast?
For the person up thread talking about learning things, I wish I was in that position today with them rather than 20 odd years ago where everyone was in the dark, and thank the heavens for sites like doom9 that shone lights in dark places!
>For the person up thread talking about learning things, I wish I was in that position today with them rather than 20 odd years ago where everyone was in the dark
Where would you start today?
And what was being circumvented? Copyright protection?
DeCSS was considered a very big no no if you worked for a company that did work for content owners. Doom9 had lots of info on how to use DeCSS, and so it was flagged by lots of corps.
Where would I start today? That depends on your level of interest, and what you want to do. Are you wanting to learn things to do to stay hip and cool making videos for the socials, or are you wanting to do technical things to video for less prestigious ends? That's two different paths that intertwine, but different recommendations depending.
That's not a rhetorical question, btw. I've been in both fields, and continue to work in both. There's lots of reading, and today watching videos, but the biggest thing will be the access to actually doing the things that weren't possible so freely 20 years ago. Try things, make mistakes, learn, do again.
I am interested in using video compression to improve delivery of VR and AR content over the web. But, this can mean a lot of different things! I know there is a lot of opportunity for this, I have a lot of ideas, but my knowledge of video compression and video streaming is limited. There are some companies working on this, but it’s not a singular problem or solution. I expect it will end up being many categories of solutions.
I usually like to learn about things from first principles so that I can then choose what to intentionally skip over, if that makes sense. I find the history is usually a good place to start, but it only goes so far with these more blackbox type topics like video compression.
There's a bunch of details that can be suggested, but the sad (actually, amazing) thing is that compression and encoding software has come such a long long way, that most of the default settings will produce a very decent result. FFMPEG + x264/x265 are stunning with minimum inputs required (minimum compared to the many many switches you can fiddle with individually).
For a broader understanding, look into the basics of how codecs like h.264/h.265 work. Learn about I frame encoding and how P and B frames work. Learn about the affects of long-GOP (multiple seconds) encodes for streaming purposes vs shorter GOPs (half second). Understand how an encoder makes it's vector decisions. How/why static videos encode compared to fast action. How will the videos you intend to use for VR/AR fall into those categories.
Resources like articles on Wikipedia have lots of information on the technical side of things without that are not video compression tutorials. However, learning the tech side will help make informed decisions on what knobs to tweak and why. There are so so many actual blogs/tutorials/SO answers/etc that will give you actual settings to apply. Once you have the specific question, I will be amazed if there is no answer available for it online.
It's all made of inter prediction + intra prediction + residual coding.
There's an evolution from JPEG -> MPEG2 -> MPEG4 part 2 (XviD) -> AVC -> HEVC… where it gets more complicated over time but that's still the structure.
There's also alternative ideas like wavelets (JPEG2000) and many other minor silly ideas; almost all of them are bad and can be ignored. Which is not to say the MPEG codecs are perfect.
ML people think they can do "ML video compression" which will be a black box; I think this might work but only because calling your video codec ML means you can make your codec 1TB instead of a few hundred KB.